REVISED DESCRIPTION (by applicant): The goal of this proposal is to develop an integrated optical system that improves the sensitivity and resolution of small-animal imaging devices. This new system will integrate recent advances in high-resolution video-transmission microscopy, laser fluid velocimetry, and laser spectroscopy. Specifically, this system will be used for imaging rat mesentery in vivo at the cellular level. This technology has a broad spectrum of biomedical applications including imaging of microlymphatic functioning in normal and pathological states and under different interventions, such as drug or radiation therapy; modeling of experimental lymphedema; optimization of laser treatment of vascular lesions, and so on. The Specific Aims are to: Specific Aim 1. Develop an integrated optical system combining transmission microscopy and laser velocimetry for highly sensitive imaging of rat mesentery structures at the cellular level. Specific Aim 2. Explore the capability of this integrated optical imaging system for studying rat mesentery microcirculation in response to therapeutic interventions. This new system will provide high contrast of mesenteric microstructures of different small animals in the visible-light range with high resolution. The most innovative features of this project include noninvasive high imaging of cellular structures in vivo, guidance of laser therapy and microsurgery, and quantitative characterization of blood and lymph microcirculation. Long-term goals are to develop 3-D imaging systems and to study laser-cell and drug-cell interactions in vivo. The technical realization of this new imaging system is relatively simple, combining transmission microscopy and laser technique already routinely in use.